PROJECT SUMMARY/ABSTRACT The primary objective of the Training Program in Hematology, in its 35th year of funding, is to train MD, MD/PhD, and PhD postdoctoral fellows interested in adult hematology for careers in academic medicine and biomedical research. Johns Hopkins Hematology is among the largest free-standing adult hematology programs. We are requesting support for four postdoctoral trainees per year, which is unchanged from the previous grant cycle. The Johns Hopkins Hematology Fellowship Program, which supports 2 single-board hematology fellows per year, is the major substrate for this T32. This fellowship program is one of only 2 programs in the United States that recruits for single-board hematology fellows, and provides dedicated training in benign and malignant hematology without training in solid tumors. Thus, the purpose of the proposed training program is to prepare qualified individuals with an MD and/or PhD degree for a research career in the field of adult hematology. The training program consists of well-funded and highly experienced investigators, most of whom are internationally recognized for their research pertaining to hematopoiesis and stem cell biology, anemias, hemoglobinopathies, thrombotic microangiopathies, bone marrow failure states and myeloproliferative diseases. Training is enhanced by an outstanding research environment with state-of-the-art research facilities and cores, outstanding faculty mentors, and an existing program project grant on bone marrow transplantation. Despite a national trend away from single board hematology fellowship programs, Johns Hopkins continues to attract outstanding MD and MD/PhD candidates for single board hematology training and prepares them for careers in biomedical research1. There is also an exceptional pool of PhD postdoctoral fellows from the labs of our basic science mentors who are well-integrated in the hematology multidisciplinary conferences and even the clinical training program. Specific aims are of this training program are: 1) to provide research training opportunities in a variety of areas pertaining to hematology including benign and malignant hematopoiesis, bone marrow failure disorders, bone marrow transplantation, stem cell biology, immunology, genetics, thrombotic microangiopathies, myeloproliferative/myelodysplastic syndromes and hemoglobinopathies 2) to provide the opportunity for structured coursework and seminars pertaining to clinical, translational and basic research pertaining to hematology, and to provide opportunities for instruction in grant writing, manuscript writing, public speaking and biostatistics 3) to allow for group mentoring, and careful monitoring of the trainees? progress and the overall success of the training program 4) to address the critical shortage of adult hematologists pursuing careers in academic hematology